1. Field of the Invention
The present invention generally relates to a developer regulator for restricting amount of developer on a developer bearer, a development device including the developer bearer and the developer regulator, and an image forming apparatus such as a copier, a printer, a facsimile machine, a plotter, or a multifunction machine capable of at least two of these functions that includes the development device.
2. Description of the Background Art
In general, electrophotographic image forming apparatuses, such as copiers, printers, facsimile machines, or multifunction devices including at least two of those functions, etc., include a latent image carrier on which an electrostatic latent image is formed and a development device to develop the latent image with developer. In development devices, a configuration in which amount of the developer carried on a developer bearer is adjusted to a suitable value by a developer regulator, and then the developer whose amount is adjusted is carried to a developing region facing a latent image carrier, is widely used.
As a developer regulator, a regulator blade formed of a resin, an elastic material, or a metal plate is widely used. A regulator blade 200 includes a bent point 200b near a distal end 200a side as shown in FIG. 1, as proposed for example in JP-2007-57883-A, JP-2007-57910-A, and JP-2000-338779-A. In this example, when toner (as the developer) carried on a development roller 300 passes a position facing the bent point 200b of the regulator blade 200 by rotating the development roller 300, and the toner is formed into a thin layer. As illustrated in FIG. 2, the amount of toner to be carried to the developing region is adjustable depending on a bending angle θ formed by the bent point 200b of the regulator blade 200 and a length A between a tip of the regulator blade 200 and the bent point 200b thereof. The amount of toner is restricted by a vicinity of an apex of an outer edge of the bent point 200b. 
However, in this example in which the bent point 200b is provided in the regulator blade 200, a contact pressure to contact the regulator blade 200 to a surface of the development roller 300 focuses on the apex of the outer edge of the bent point 200b, which increases the friction between the development roller and the regulator blade and causes the development roller 300 and the regulator blade 200 to abrade. As a result, it is difficult to maintain the toner layer on the development roller restricted by the regulator blade at a consistent thickness over time.
In order to alleviate the abrasion at the bent point, it is conceivable that a contact pressure between the regulator blade and the development roller is reduced. However, when the contact pressure is reduced, the charging ability of the toner is reduced as well, with concomitant imaging failure such as black spots in the background of the image.
Alternatively, when the toner charging ability is increased so as to prevent the occurrence of black spots, fluctuation in usage environment (toner amount of the development roller) and in durability of the development roller becomes larger over time.